package org.dfg.corejava.jdk7.aio.chatserver;

/*
 * Copyright (c) 2011 Oracle and/or its affiliates. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * - Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 * 
 * - Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * 
 * - Neither the name of Oracle nor the names of its contributors may be used to
 * endorse or promote products derived from this software without specific prior
 * written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * This source code is provided to illustrate the usage of a given feature or
 * technique and has been deliberately simplified. Additional steps required for
 * a production-quality application, such as security checks, input validation
 * and proper error handling, might not be present in this sample code.
 */

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousSocketChannel;
import java.nio.channels.CompletionHandler;
import java.util.LinkedList;
import java.util.Queue;
import java.util.concurrent.atomic.AtomicReference;

/**
 * Client represents a remote connection to the chat server. It contains methods
 * for reading and writing messages from the channel. Messages are considered to
 * be separated by newline, so incomplete messages are buffered in the
 * {@code Client}.
 *
 * All reads and writes are asynchronous and uses the nio2 asynchronous
 * elements.
 */
class Client {
	// 该客户端对应的连接
	private final AsynchronousSocketChannel channel;
	private AtomicReference<ClientReader> reader;
	private String userName;
	// 缓存未发送的信息
	private final StringBuilder messageBuffer = new StringBuilder();
	// 消息发送队列
	private final Queue<ByteBuffer> queue = new LinkedList<ByteBuffer>();
	private boolean writing = false;

	public Client(AsynchronousSocketChannel channel, ClientReader reader) {
		this.channel = channel;
		this.reader = new AtomicReference<ClientReader>(reader);
	}

	/**
	 * Enqueues a write of the buffer to the channel. The call is asynchronous
	 * so the buffer is not safe to modify after passing the buffer here.
	 *
	 * @param buffer the buffer to send to the channel
	 */
	private void writeMessage(final ByteBuffer buffer) {
		boolean threadShouldWrite = false;

		synchronized (queue) {//由于是异步的，可能会同时接受多个其他客户端的消息，所以要使用队列
			queue.add(buffer);
			// Currently no thread writing, make this thread dispatch a write
			if (!writing) {
				writing = true;
				threadShouldWrite = true;
			}
		}

		if (threadShouldWrite) {
			writeFromQueue();
		}
	}

	// 把队列中消息发送给客户端
	private void writeFromQueue() {
		ByteBuffer buffer;

		synchronized (queue) {
			buffer = queue.poll();
			if (buffer == null) {// 如果已经没有数据，则停止写出
				writing = false;
			}
		}

		// No new data in buffer to write
		if (writing) {
			writeBuffer(buffer);
		}
	}

	private void writeBuffer(ByteBuffer buffer) {
		channel.write(buffer, buffer, new CompletionHandler<Integer, ByteBuffer>() {
			@Override
			public void completed(Integer result, ByteBuffer buffer) {
				if (buffer.hasRemaining()) {
					channel.write(buffer, buffer, this);
				} else {
					// Go back and check if there is new data to write
					writeFromQueue();
				}
			}

			@Override
			public void failed(Throwable exc, ByteBuffer attachment) {
			}
		});
	}

	/**
	 * Sends a message
	 * 
	 * @param string the message
	 */
	public void writeStringMessage(String string) {
		writeMessage(ByteBuffer.wrap(string.getBytes()));
	}

	/**
	 * Send a message from a specific client
	 * 
	 * @param client the message is sent from
	 * @param message to send
	 */
	public void writeMessageFrom(Client client, String message) {
		if (reader.get().acceptsMessages()) {
			writeStringMessage(client.getUserName() + ": " + message);
		}
	}

	/**
	 * Enqueue a read
	 * 
	 * @param completionHandler callback on completed read
	 */
	public void read(CompletionHandler<Integer, ? super ByteBuffer> completionHandler) {
		ByteBuffer input = ByteBuffer.allocate(256);
		if (!channel.isOpen()) {
			return;
		}
		channel.read(input, input, completionHandler);
	}

	/**
	 * Closes the channel
	 */
	public void close() {
		try {
			channel.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	/**
	 * Run the current states actions.
	 */
	public void run() {
		reader.get().run(this);
	}

	public void setUserName(String userName) {
		this.userName = userName;
	}

	public void setReader(ClientReader reader) {
		this.reader.set(reader);
	}

	public String getUserName() {
		return userName;
	}

	public void appendMessage(String message) {
		synchronized (messageBuffer) {
			messageBuffer.append(message);
		}
	}

	/**
	 * @return the next newline separated message in the buffer. null is
	 *         returned if the buffer doesn't contain any newline.
	 */
	public String nextMessage() {
		synchronized (messageBuffer) {
			int nextNewline = messageBuffer.indexOf("\n");
			if (nextNewline == -1) {
				return null;
			}
			String message = messageBuffer.substring(0, nextNewline + 1);
			messageBuffer.delete(0, nextNewline + 1);
			return message;
		}
	}
}
